For reliable internet traffic delivery via a Multi-Protocol Label Switching (MPLS) network it is important to reduce delay due to connectivity failure. Internet Engineering Task Force (IETF) Request for Comments (RFC) 5880, entitled Bidirectional Forwarding Detection (BFD), describes a low latency protocol for detecting faults in bidirectional paths between two forwarding engines, such as faults within interfaces, data links and the like between network elements or nodes. BFD operates independently of media, data protocols, and routing protocols.
Thus, BFD provides a mechanism to quickly detect connectivity failure so that an alternate connectivity path can be used to restore communication. To detect a data plane failure in the forwarding path of an MPLS Label Switched Path (LSP), a BFD session is established for that MPLS LSP. If the LSP is associated with multiple Forwarding Equivalence Classes (FECs), a BFD session is established for each FEC. BFD control packets are transmitted by the ingress LSR; these packet travel along the same data path as the LSP being verified and are processed at the egress LSR. BFD control packets contain a “discriminator” field to distinguish each BFD session on the LSP. A BFD session is established by sending the BFD session parameters from the ingress LSR to the egress LSR. Unfortunately, BFD cannot presently be used within the context a Multi-Protocol Label Switching (MPLS) network including unnumbered interfaces or links (i.e., interfaces or links that do not have IP addresses).